In recent years, there is an increasing demand for technologies for removing specific proteins, leukocytes, toxins, and the like contained in body fluids of patients to be applied to an extracorporeal circulation blood purification therapy of curing autoimmune diseases, such as systemic lupus erythematosus, chronic or malignant articular rheumatism, multiple sclerosis, chronic ulcerative colitis, and Crohn's disease, as well as other diseases such as sepsis, inflammatory bowel disease, leukemia, and cancer, or for immunity control before an organ transplant operation.
High reliability to safety as a medical device apparatus, not to mention high removing capability of the materials to be removed, is required for a body fluid-treating filter device used in these applications. For example, as a leukocyte-removing filter apparatus well known as an example of the above filter apparatus, a flat-type filter device in which nonwoven fabric made from ultra-thin fibers or a filter device equipped with a housing packed with a filter material wound in a cylindrical form (for example, Patent Document 1) are widely used.
A structure of a body fluid-treating filter device will be outlined. FIGS. 6 and 7 show commonly used typical flat-type or cylindrical-type body fluid-treating filter devices. In the figures, a body fluid-treating filter layer 12 formed in the form of a flat plate or a cylinder is housed in a housing 11.
In the cylindrical body fluid-treating filter device of FIG. 7, one end of the filter layer 12 is completely sealed with a dish 16, the other end of the filter layer 12 is liquid-tightly secured to the inside of the lid 18, which has a body fluid flow port 52, and the hollow section 20 of the filter layer 12 communicates to the outside of the device.
If the body fluid to be treated is introduced in this structure from the body fluid flow port 51 (in this case, a body fluid inlet port), the body fluid flows through the filter layer 12 and is sent to the outside from the body fluid flow port 52 (in this case, a body fluid outlet port), while filling the void between the inner wall of the housing 11 and the surface of the filter layer 12. Arrows in the Figures indicate the directions in which the body fluid flows.
In some cases, the device may be operated by causing the body fluid to flow in the directions opposite to the direction of the arrows. In these embodiments, if the body fluid is introduced from the body fluid flow port 52 (in this case, a body fluid inlet port), the body fluid flows through the filter layer 12 and is sent to the outside from the body fluid flow port 51 (in this case, a body fluid outlet port), while filling the void between the inner wall of the housing 11 and the surface of the filter layer 12.
When such a body fluid-treating filter device is actually used, the pressure in the device increases in some cases depending on the state of the blood to be treated, for example, when the amount of a blood anticoagulant added is insufficient or the blood anticoagulant is mixed only insufficiently. In other cases, when a physiological solution is caused to flow in order to recover the blood from the filter device, the physiological solution does not necessarily flow through the entire filter device, resulting in insufficient recovery of the body fluid. In particular, in the flat-type body fluid-treating filter device of FIG. 6, there was a problem of uneven flow of the body fluid introduced from the body fluid flow port 51, since such a body fluid flows through the void between the inner wall of the housing 11 and the surface of the filter layer 12, while spreading two dimensionally.
In addition, a filter device containing a body fluid-treating filter material cylindrically wound around a core pipe having a porous section has been disclosed (Patent Document 2). Although this filter device has an effect of efficiently filling a body fluid-treating filter in a housing, countermeasures against the pressure increase and blood poor recovery were still insufficient since the essential structure remained the same as above.
As mentioned above, commonly used fluid-treating filter devices have problems besides basic performance that should be still improved as a medical apparatus.    [Patent Document 1] JP-A-62-243561    [Patent Document 2] JP-A-9-239022